Mobile communication devices have become increasingly common in current society. The prevalence of these mobile communication devices is driven in part by the many functions that are now enabled on such devices. Increased processing capabilities in such devices means that mobile communication devices have evolved from being pure communication tools into sophisticated mobile multimedia centers that enable enhanced user experiences.
The redefined user experience requires higher data rates offered by advanced wireless communication technologies, such as long-term evolution (LTE) and fifth-generation new radio (5G-NR). To achieve the higher data rates in mobile communication devices, power amplifiers (PAs) may be employed to increase output power of radio frequency (RF) signals (e.g., maintaining sufficient energy per bit) communicated by mobile communication devices.
PAs are inherently nonlinear. The nonlinearity generates spectral re-growth that can lead to adjacent channel interference and/or in-band distortion. As a result, the RF signals outputted by the PAs may violate regulatory out-of-band emission requirements and/or suffer an increased bit-error-rate (BER). To help reduce nonlinearity, the PAs may be configured with a relatively large back-off so as to operate within a linear portion of a PA's operating curve. However, the RF signals transmitted in LTE and 5G-NR systems typically have higher peak-to-average ratios (PARs). In this regard, the back-off needs to be well below maximum saturated output power of the PA to handle sporadic high peaks of the RF signals. As a result, the PAs may be forced to operate with very low efficiency (e.g., less than 10%), with a large portion of the PA power (e.g., 90%) being turned into thermal heat.
Envelope tracking is a power management technology designed to improve efficiency levels of PAs to help reduce power consumption and thermal dissipation in mobile communication devices. As the name suggests, envelope tracking employs a system that keeps track of the amplitude envelope of the RF signals communicated by mobile communication devices. The envelope tracking system needs to constantly adjust supply voltage applied to the PAs to ensure that the PAs are operating at a higher efficiency.